Anyone built a Gainclone?

Heya,

Has anyone here built a GainClone? If you don't know, it's a 50W power amp built around an LM3875 opamp. The thing is there seem to be a million different designs around, some put together by people who sound like they might be audiophools (everheard of removing the cases of caps and replacing them with blu-tac??) but I don't really know... Will there really be any sound difference between using the opamp in inverting or non-inverting??

Anyway, I thought maybe someone here might have built one of these or even have a PCB layout they might wanna share :grin: or at least have some advice to share about which version to build. So uhhhh yeah, anyone know anything about these amps?

Thanks a lot!

Hi Nat,

No, I haven't built the GainClone itself, but I've done a lot of the LMxxxx power amp IC circuits. The only advice I can give you is get to the LM3875 Home Page and grab yourself the PDF Datasheet and have a play with the application circuits.

These circuits have a nice habit of working really well! because they will have been designed and tested by the apps engineers, and are really a "product on a plate" ready for designers to take and use in their own products/designs. Once you've made the basic circuit and passed signal, you can then mod it to your hearts content!

I think a crucial part of any of these IC power amps is the layout of the PCB. Use PSU decoupling caps near the IC, and have thick 0V and supply traces. Other than that, it's just listening and testing! (Oh, and I'd advise you not to use blu-tack to replace capacitor cases. Everyone knows Edam is the only way to go!! :green: :shock: :wink: )

Mark

A friend did it. You will get surprised about how simple it is and now good it is.
My LMs are laying around, plan to make mine soon.

cheers!

Hi Nat!

I haven't built a gainclone but I am also looking at different power amps for my monitoring.

Have you been to the chipamps forum at www.diyaudio.com ???

There is loads of info over there about the gainclones, the Nelson Pass forum seems to have some of the best stuff there but a lot more complicated than the gainclone.

I think Nelson Pass has just produced a few pdf's about applying his ZEN ideas to a chip amp ala gainclone. Might be worth a look and could be a considerable improvement.

Cheers Tom

I built a pair. I used Scott Nixon's boards:

http://www.scott-nixon.com/dac.htm

I've also built his tubedac kit. Simple and neat. Sounds good. haven't got much to compare it to, though.

The Gainclone amps are really good for as cheap and simple they are. I used Plitron toroids for power, with separate negative and positve supplies.

I built the inverting version. I was going to build a non-inverting version and compare, but the first one sounded so good I decided to stop tinkering.

As to how good it is, there are a lot of superlatives thrown around about this circuit, as to what other amp got blown away by so and so's Gainclone. I don't like to participate in that stuff; we're all biased about the stuff we build.

What I will tell you is this amp is a cheap and lazy guy's dream. The parts are cheap (don't skimp on the power supply, though.), you don't have to come up with some awesome heatsink, ala Nelson Pass's Zen, and assembly is a couple of hours. The sound will surprise you after a lazy afternoon of soldering and bolting together.

-neil

I tried it. Boring piece of chip shite. But that's just my personal experience. I know there are thousands of people who dig 'em..

As said above, this is THE forum for GainClones;

www.diyaudio.com/forums/forumdisplay.php?s=&forumid=40

Hey - I just built one! Very simple circuit and sounds great :thumb:










:guinness:

[quote author="daArry"]
[/quote]
What's this board for?

And it looks like the box is a recycled something?

The PCB/schematic for my version is here: http://stiftsbogtrykkeriet.dk/~mcs/LM3875/
I'll take some pictures when the boards arrive in a couple of days.

Best regards,

Mikkel C. Simonsen

[quote author="mcs"]I'll take some pictures when the boards arrive in a couple of days.[/quote]

Cool Mikkel..
do you plan to have some spare pcbs to sell?
it could be a really easy and interesting project.
Let us know :thumb:

What's this board for?

Click to expand...

+/-15V, balanced rcv circuit (INA134)...

And it looks like the box is a recycled something?

Click to expand...

Yup, it was an old 40's radio prior...where the big knob is, is where the tuning section was before, and the panel next to it was where the speaker wudda been...

...when the boards arrive in a couple of days.

Click to expand...

Is there a certain PLL brd in that delivery too? :wink:

Peesh

It's very simple and sounds nice.

[quote author="kruz"]do you plan to have some spare pcbs to sell?
it could be a really easy and interesting project.
Let us know :thumb:[/quote]
Yes, if it works as intended I can make some more boards.

[quote author="daArry"]Is there a certain PLL brd in that delivery too? :wink:[/quote]
There should be - I ordered it at least.

Best regards,

Mikkel C. Simonsen

Interesting that those chips use a quasi-comp output stage. (Actually, I think this is the general rule with chip amps; it probably was something to do with power NPNs being easier to fabricate on the wafer or somethin' like that). During my brief time in hi-fi repair, I always felt that quasi-comp outputs generally sounded better--but I never took the time to investigate it scientifically. It could have just been my imagination.

Chip amps can sound very good. My living room system is an old Japanese integrated amp with one of those STK "packs" (as we called them) driving an ancient pair of Cambridge 3-ways with replaced woofers and midrange drivers. It sounds good to me, smooth and tight with good "air" (as the audiophools say) in the treble range.

Here's my board:



I haven't tested it yet (there are no diodes as you can see). RS should have sent me those on Tuesday, but they didn't. I should receive them on Monday (or so they told me).

I'll make some tests and measurements then...

Best regards,

Mikkel C. Simonsen

cool mikkel!!!
keep us informed.. i'd really like to buold me one for sure :thumb:

Hell, yeah! :thumb: Let us know how it works, and then give us the details.

Bear

I thought I would have time to test it before my holiday, but of course I didn't... I installed the diodes, but that's how far I got.

So you will get the complete report and test results in about two weeks...

If anybody's interested in PCBs, I'll check the cost when I get back. How about IC's? I can get the LM3875 at a price that's (much) better than Farnell's from the Danish National distributor - but the minimum quantity is 120 pcs. Anybody interested in a group buy?

Best regards,

Mikkel C. Simonsen

Mikkel, i'm interested in the pcb and probably also for those LM3875..
Let me/us know how it goes :grin:
Have a nice holiday :thumb:

Hell, I'm lazy. If you want to price out boards and chips, even a completish kit to populate them, I'd be interested.

Bear

Uh, ok, I'm dumb-what is it? A preamp for an unbalanced signal?
Joel

Oh OK, got it...